The invention relates to an exhaust air dryer having a housing enclosing an inner space, it being possible for a drying chamber for items to be dried, a supply air duct between a first supply air inlet and the drying chamber for supply air, a heater for heating the supply air in the supply air duct, a fan with which the heated supply air can be guided through the drying chamber, and an exhaust air duct between the drying chamber and an exhaust air outlet on the housing for exhaust air, to be arranged in the inner space.
Such an exhaust air dryer is disclosed in DE 30 00 865 A1.
In general, a washer dryer is designed and operated as an exhaust air drier or a condensing dryer. In order to absorb moisture, an exhaust air dryer generates warm process air which is blown through the washing to be dried and then removed from the washer dryer. In any case, for the removal when the exhaust air dryer is installed inside a building, a suitable exhaust air hose must be used, by which the moisture-laden process air is conveyed out of the building—whether directly or via a permanently installed exhaust air duct. A condensing dryer whose mode of operation is based on the condensation of the moisture from the laundry vaporized by means of warm process air, requires no exhaust air hose and facilitates energy recovery from the heated process air, for example by use of a heat pump.
In general however, in the case of an exhaust air dryer, after passing through a washing drum the moisture-laden air is conveyed out of the dryer, it not being possible for energy recovery to take place. An exhaust air dryer with heat recovery is nevertheless known from DE 30 00 865 A1. In this exhaust air dryer ambient air (for example at 20° C. and 60% relative humidity: so-called supply air) flowing along heat exchanger surfaces of an air-air heat exchanger is heated at that point during cooling of the warm process air coming from the drying chamber, which likewise passes through the heat exchanger. Dependent on the cooling capacity or heat exchange, condensate is produced and collected in a container (condensate trough) or pumped away.
In this known dryer a fan is used to convey the process air (supply air or exhaust air). In addition, known dryers generally have only one motor which drives both the rotatable drying chamber (washing drum) and the fan.
Finally, devices are known in dryers which are intended to influence the conduction of the process air. DE 43 06 217 B4 describes a program-controlled washer dryer in which the process air is guided by means of a fan in a closed process duct in which specially arranged closing devices are located. The closing devices are appropriately actuated dependent upon the operating state (heating phase, washing-drying phase, attainment of the maximum permissible temperature).
With an exhaust air dryer it is often desirable to be able to use the longest possible exhaust air line or longest possible exhaust air hose in order to have more flexibility with regard to the installation of the dryer where the exhaust air is not intended to be output to the inside of the installation room.